How does commit 47ec340c not introduce a bug?

Uwe Kleine-König
2013-05-07T09:24:28Z

Hello,

On Tue, May 07, 2013 at 04:17:34AM -0500, Robin Holt wrote:
> I noticed a warning while cross-compiling all arm defconfigs.
>
> The mmp2_defconfig gave this warning:
>
> drivers/video/backlight/max8925_bl.c: In function 'max8925_backlight_probe':
> drivers/video/backlight/max8925_bl.c:177:3: warning: statement with no effect [-Wunused-value]
>
> This appears to have been introduced by the above commit when !CONFIG_OF
>
> Looking at this more closely, I am not sure how this was ever intended
> to be handled or how the errors returned in the CONFIG_OF case were
> intended to be handled as the return from max8925_backlight_dt_init is
> always ignored.
>
> I think this needs some more attention, but do not feel like I know
> enough about it or have any means to test it to weigh in.
>
> Thanks,
> Robin
>
>
> commit 47ec340cb8e232671e7c4a4689ff32c3bdf329da
> Author: Qing Xu <qingx@marvell.com>
> Date: Mon Feb 4 23:40:45 2013 +0800
>
> mfd: max8925: Support dt for backlight
>
> Add device tree support in max8925 backlight.
>
> Signed-off-by: Qing Xu <qingx@marvell.com>
> Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
> Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
>
> diff --git a/drivers/video/backlight/max8925_bl.c b/drivers/video/backlight/max8925_bl.c
> index 2c9bce0..5ca11b0 100644
> --- a/drivers/video/backlight/max8925_bl.c
> +++ b/drivers/video/backlight/max8925_bl.c
> @@ -101,6 +101,29 @@ static const struct backlight_ops max8925_backlight_ops = {
> .get_brightness = max8925_backlight_get_brightness,
> };
>
> +#ifdef CONFIG_OF
> +static int max8925_backlight_dt_init(struct platform_device *pdev,
> + struct max8925_backlight_pdata *pdata)
> +{
> + struct device_node *nproot = pdev->dev.parent->of_node, *np;
> + int dual_string;
> +
> + if (!nproot)
> + return -ENODEV;
> + np = of_find_node_by_name(nproot, "backlight");
> + if (!np) {
> + dev_err(&pdev->dev, "failed to find backlight node\n");
> + return -ENODEV;
> + }
> +
> + of_property_read_u32(np, "maxim,max8925-dual-string", &dual_string);
> + pdata->dual_string = dual_string;
> + return 0;
> +}
> +#else
> +#define max8925_backlight_dt_init(x, y) (-1)
It's probably best to make this:

static inline max8925_backlight_dt_init(struct platform_device *pdev,
struct max8925_backlight_pdata *pdata)
{
return -ENODEV;
}

> +#endif
> +
> static int max8925_backlight_probe(struct platform_device *pdev)
> {
> struct max8925_chip *chip = dev_get_drvdata(pdev->dev.parent);
> @@ -147,6 +170,13 @@ static int max8925_backlight_probe(struct platform_device *pdev)
> platform_set_drvdata(pdev, bl);
>
> value = 0;
> + if (pdev->dev.parent->of_node && !pdata) {
> + pdata = devm_kzalloc(&pdev->dev,
> + sizeof(struct max8925_backlight_pdata),
> + GFP_KERNEL);
> + max8925_backlight_dt_init(pdev, pdata);
> + }
> +
> if (pdata) {
> if (pdata->lxw_scl)
> value |= (1 << 7);
> @@ -158,7 +188,6 @@ static int max8925_backlight_probe(struct platform_device *pdev)
> ret = max8925_set_bits(chip->i2c, data->reg_mode_cntl, 0xfe, value);
> if (ret < 0)
> goto out_brt;
> -
> backlight_update_status(bl);
> return 0;
> out_brt:
>
> _______________________________________________
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> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

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